In some thin displays such as liquid-crystal displays, a retardation film is used. The retardation film has a slow axis, and has an action to generate phase lag of the polarization component parallel to the slow axis of the light having passed through the retardation film (hereinafter this may be arbitrarily referred to as “in-plane retardation”).
As combined with a polarizing film capable of producing linear polarization in the direction vertical to the absorption axis thereof, the retardation film is used for prevention of external light reflection on a display surface and for optical compensation for viewing angle enlargement. In this case, the slow axis of the retardation film and the absorption axis of the polarizing film must be so arranged as to form a predetermined angle therebetween.
In addition, the retardation film may be required to satisfy so-called reversed wavelength dispersion characteristics of such that the retardation thereof increases with the increase in the wavelength of light applied thereto. As an example of the retardation film having reversed wavelength dispersion characteristics, Patent Document 1 discloses a retardation film web formed through longitudinal monoaxial stretching, transverse monoaxial stretching, longitudinal and transverse simultaneous biaxial stretching or longitudinal and transverse successive biaxial stretching.